There is a technique known in the art for removing the background color (base color) from a target image represented by image data. One advantage of removing the background color before printing the target image is that less printing agent (ink, toner, or the like) is required for printing the target image than when the background color is not removed.
According to one process of removing the background color from a target image described in the art, an image processor removes parts of the image whose gradation values fall within a specified removal range by converting the colors in these image parts to white, and corrects gradation values that fall within a specified adjustment range near the removal range in order to maintain continuity of tones within the image after the removal process is completed. This process can smooth out differences in gradation levels produced in bordering regions between background images, whose background color has been removed, and object images.